. >> claudia is a hydrologist. >> is it completely unrealistic to think of these deep level aquifers at just an unlimited resource? >> we are lowering the water levels lower than historic lows, taking more out than recharging the system. >> there is more than the immediate impact of all this well digging, land subsidence. >> it is the lowering of the land surface. >> michelle tracks how much is occurring and where. >> this is a canal. as subsidence occurs, the road lowers, the water is starting to run into part of the bridge. >> the water is veering this way. >> the water's going this way and all of these items are shoved up against the bridge instead of flowing underneath the bridge if there was space between the water surface and bridge. >> you can see that. >> most alarming is that subsidence permanently changing an aquifer's ability to hold water. >> it can hold less water than it did before subsidence. that is forever. that is permanent. >> coming up on tech know, using the sun to turn waste water into liquid gold. >> ok. >> we want to hear what you think about these stories. jo